Field of the Invention
This invention relates to a method and apparatus for testing for the presence, brightness and/or color of a light emitting diode (LED) in a printed circuit board, where the LED is biased either with constant current or with a current pulse.
Description of Related Art
Printed circuit boards typically contain multiple components including: LEDs, resistors, capacitors, diode, fuse, processors, and similar such components. LEDs are often used as external signals, internal diagnostics and for other suitable applications. Typically, verification of the operation of a printed circuit board having LEDs required powering up a fully rendered printed circuit board and manually verifying the operation of the LEDs. Alternatively, a test fixture may be constructed including bulky and expensive fiber optics that extend between the printed circuit board to be tested and a test system.
Verification of the presence and operation of LEDs within a printed circuit board may be accomplished without a power supply such as described in U.S. Pat. No. 6,490,037, issued to Schmitt, which is hereby incorporated by reference in its entirety in a manner consistent with the present document. Further, verification of the presence and operation of LEDs within a printed circuit board may be accomplished such as described in U.S. Pat. Nos. 7,023,554; 7,227,639; and 7,265,822, each issued to Schmitt, which are also each hereby incorporated by reference in their entirety in a manner consistent with the present document. However, these known methods require a constant current for a sampling period.
Determination of the color and brightness of the LEDs, beyond mere verification, typically requires extensive calibration and set-up to align sensors with the LEDs and run the wiring necessary for sending numerous signals to determine such parameters of the LEDs.